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Genetic and Rare Diseases Information Center (GARD)

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Glycine encephalopathy

Other Names for this Disease
  • Glycine synthase deficiency
  • Hyperglycinemia nonketotic
  • Nonketotic hyperglycinemia
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Your Question

Is it necessary to restrict protein intake in children that have this disorder? If so, what are the risks if protein intake is not restricted?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

How might glycine encephalopathy be treated?

Currently there is not a cure for glycine encephalopathy.[1][2] All but very mildly or atypically affected individuals develop intellectual disability and seizures, even with treatment. Treatment options for people with glycine encephalopathy may vary depending on the severity of their condition. Tests, such as MRI and EEG, as well as evaluations of development and neurological function can help determine the severity of the condition in an infant, child, or adult.[1]

The goal of treatment is to reduce the amount of glycine in the plasma (blood). Treatment may involve a medication called sodium benzoate, which binds with glycine allowing it to be passed out in the urine, and dextromethorphan, ketamine, or felbamate, which block some of the harmful effects of excessive glycine. These treatments may help control seizures, increase alertness, and in mildly affected individuals, improve behavior.[1]  Drug dosage must be individually tailored and requires regular and careful monitoring.[1][2] Studies regarding the effectiveness of these treatments are ongoing.[1] Mildly affected individuals may receive the greatest benefit from treatment, particularly if treatment is started early.[1]

Other treatments include drugs to control seizures (anti-epileptic drugs); assistive devices or surgeries to aid with feeding and swallowing (e.g., gastrostomy tube); physical therapy; and scoliosis management. Parents and family members may benefit from genetic counseling. Click here to learn more about genetic consultations.[1]

For further details on treatment, please visit the following link to GeneReviews. GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions. Because of the complexity of the information in the article, we recommend that you review it with a health care provider.

Last updated: 11/10/2011

Is protein restriction recommended for people with glycine encephalopathy?

Diet restriction alone has not been shown to be effective in improving symptoms of glycine encephalopathy. It is no longer used as a primary method of treatment. Glycine restricted diet in combination with sodium benzoate may be helpful for treating people with severe forms of the condition (who require the maximum or near maximum dose of sodium benzoate).[2] If you have questions or concerns regarding treatment we strongly recommend that you discuss them with a healthcare provider.
Last updated: 8/26/2011

How can I find a genetics professional in my area?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:
Last updated: 10/18/2013

  • Hamosh A, Scharer G, Van Hove J. Glycine encephalopathy. GeneReviews. November 2009. ; Accessed 11/10/2011.
  • Van Hove JL, Vande Kerckhove K, Hennermann JB, Mahieu V, Declercq P, Mertens S, De Becker M, Kishnani PS, Jaeken J. Benzoate treatment and the glycine index in nonketotic hyperglycinaemia. J Inherit Metab Dis. 2005;28(5):651-63; Accessed 8/26/2011.